Nickfromwales

You can say "Thermal Mass" as many times as you want, it's fine; we all know what we mean / what is meant / time to move (not necessarily swiftly) on.... Becoming energy rich in the summer will allow you to 'bank' for the winter, so a well-performing dwelling will still be manageable in terms of energy / costs aka "green credentials". Solar plus batteries here should be a no-brainer, but even without these a heat-pump based space heating system will make running costs 'acceptable' vs the alternatives. Maybe sacrifice the renewables at the outset to get more spaces with plaster & paint + floor coverings, and just cable for the solar et-al during 1st fix? 10 years is a long time to be looking at very unfinished areas, plus the cost of the renewables buys a lot of m2 of boards etc. Your choice of course, just saying... Airtightness will be of paramount importance with a dwelling this size, but you will need a very good 'team' around you to design out the multiple function living modes of this arrangement (I'll call it that vs a house, if I may ). Having a passive raft or similar long thermal time constant store and 'emitter' will offer huge dividends, so avoid skinny screeds over insulation wherever possible; another place to 'bank' cheap energy. Your architect is a good sort, as ploughing loads of expensive resources into cooling is the anti-energy efficient model you crave. Having a considerable cooling demand is way worse than a massive heating demand, IMHO, as I would much rather be slightly cold than slightly "too warm"; you can get cozy but you cannot escape excess heat. Consider solar-reflective glazing, or even better, solar (external) blinds / shutters. The latter will massively reduce summer overheat issues but will retain maximum solar gain for the winter months. As far as construction method I am a huge fan of Nudura, and it was a no-brainer for the build I am undertaking this year (for a client); 1800m2 over 4 stories (580m2 basement + GF, FF, 2F) and as you say, getting smaller as it rises. You have (again IMHO) chosen well there, for this particular instance. However, with the way it sounds like you're 'arrangement' is set out, do not discount timber frame above ground. MBC's twin-wall frame with blown cellulose is a fantastic solution, with outstanding acoustic deadening / great levels of insulation to boot. I am not a fan of SIP's at all, and would have this as a budget driven, last option. Horribly acoustically transparent. Please avoid this for your roofs wherever possible.

You talk to building control They don't bite mate! They will tell you what's needed etc and will help you to the finish line.

As the rooms will be leaking air in from outside, the MVHR would be a very bad idea IMO, and the likelihood (as the fan will need to run 24/7/365) is you will go backwards not forwards in terms of benefit. You may as well leave these bits of heat ebb into the heated envelope and go towards the space heating demand, and then deal with air quality in the study as you best see fit. When you calculate the very minimal heat recovery vs sucking in constant cold air from outdoors, I cannot see the numbers adding up. Spend the money on draft proofing and possibly filling cavities with insulation to improve the overall heat loss of the house, and that should be a far better bang for the bucks

I'd say he just wants to do a proper, thorough job tbf. And it would be many hours of testing to be thorough. It's also not great work, to come in and test someone else's work (especially a non-qualified home owner aka DIY'er) and then put your name to it. I would do as he suggested and go the BC route, if you are capable of completing the works?

He wants something for the filler to be able to be packed in against, so @Onoff's suggestion is kosher. Just foam it, leave to cure, scape back the foam to leave the depth of the plasterboard as the void, and then fill. Best to primer the cut edges of the plasterboard with 50/50 pva/water first so the filler has something to key to.

If the bends are tight, you may still want to install a conduit for the duration of the bend only, to alleviate any sounds from 'creep' where the pipe expands when suddenly heated. If very tight, just install a 90o bend and play safe. Avoiding joints is great, but having to install some and knowing where they are is plenty good enough. Hep joints are bombproof, fear ye' not....

I foam in sleeves made from 25mm flexible conduit, and then pull the pipes through them. If that needs to be sealed up, squirt some CT1 around the pipe where it exits the sleeve.

Do NOT allow the hep to drag along the cut board, as these linear scratches are #1 cause of leaking joints. Can you install sleeves of 21.5mm overflow pipe in, and then slide the hep through them?

Yup. Makes the pan move about, and leaves a bigger gap to cosmetically seal around. Looks shart IMHO, and you'll defo notice how easy it is for the pan to be moved. "Don't do it"....

Nope lol, just crazy busy as works just exploded. I don’t straddle the grout lines so the glass is sat on a uniform tile, vs sat across 2 which won’t be perfectly level. Prop OTT, but the toughened glass is quite intolerable of point loading / contact, so best safe than sorry afaic.

It’s all good. Many ways to skin a cat. @Thorfun I will never refer you to the man of dubious grout colours. Stick with me lol. Just been absolutely crazy busy with work lately, shouldn’t complain, so I may have to get @Pocster to temp for me now and then

Just plan well ahead if inserting the reducers directly into the manifold, as they are a pita to remove. If there’s any doubt, use a 150mm long piece of copper pipe inserted into the manifold so you can get the clip on removal tool in play. Prob then best to use a ‘socket’ reducer vs ‘spigot’ to save having to buy a coupler. https://www.screwfix.com/p/hep2o-plastic-push-fit-reducing-coupler-15mm-x-10mm/7165f?ref=SFAppShare

Agreed, in principal.... but the price of a borehole is high. Would need estimating by the OP before we could vote / offer feedback on that. Yes, an immersion can work here. I'd probably swap the buffer out for a unit with the capacity to take 2x 3kW immersions, it would be a lot for 1 to take on and then you'd be stuck with a single point of failure (for the sake of bit more capital investment). I've installed several immersion based heating systems (temporary and permanent) and they work brilliantly, for cheap as chips money in installation costs, but you are then tied to a 1:1 running cost. Not really a huge issue when you look at bank-rolling this endeavour, and at how much electricity you can buy with the change!! More ammunition for changing the buffer would be to fit a much bigger one (500L) to utilise load shifting off a cheap rate tariff like E10.

Gordon Lewis is your man, you should be able to get contact info for him here https://www.houseplanninghelp.com/hph195-what-is-cellulose-insulation-with-gordon-lewis/ as I cannot remember his trading name sorry! I'll need him myself soon!

Looks like it will function fine if installed as per the diagram tbh, just down to how well the boiler can modulate / cope with low heat loads (when the rooms get up to temp).

The 3 port valve is a diverter and not a mid-position, so will only have the 3 wires (brown, blue, green/yellow) so looks correct at a glance. It simply gets energised to change state (central heating or hot water) so defo isn't a 4 or 5 wire valve . +1, get on the phone and get them both back immediately and tell then if can't make it work you want a refund so you can pay someone who can. Sounds like a wiring / configuration issue to me, but really hard to say from afar.

Defo get the power on and be 100% ready to fill and keep it on! I commissioned one in the arse of last winter and it locked out a number of times and froze solid....was a right PITA tbf Turns out it was just the flow rate set too high, but trying to reinstall the popped hoses with numb hands was 'pure bliss'

Get ready to grab your tickets for the January show!

Indeed. Odd way they’ve gone about it!! Wont budge though, but should have been cordoned off not left open to access by the clients Steptoe & Sons building Co. at best.

You have more chance of meeting the pope. As an ex installer, I noted that they were very difficult to get technical information out of, and were diabolically bad at responding to clients (unless there was an online (ergo it had an element of 'public awareness') matter which got seen to in the wink of an eye.........) They now actively avoid engaging with the public, and do not attend public shows / events AFAIK (other than trade events for bulk sales).

Manufacturers state so, I guess because heat rises and the shape doesn't lend itself to having a lot of volume over the highest part of the coil. A few installation drawings show a stratification pump (a bronze pump which goes between the hot outlet and the cold inlet, triggered when the ASHP is running in DHW mode) which stirs the cylinder up and should give very good results.

If you have surplus, then absolutely perfect! Just to get a little acoustic decoupling, but a well designed system should already have this consideration included inherently, eg slightly oversized unit & lower fan speeds etc. Belt & 2 braces is always good when something makes noise / sound / vibrates, and I could think of nothing worse than choosing a cheap Chinese MVHR and putting it in the attic of your new TF home to find out it is really nasty and audible. Literally NOTHING worse than that happening. Sleep is precious!

Won’t do torque, specifically, but also won’t break your wrist. Will be quite a beast for general boat building imho. If you remove the impact element, there are plenty of cheap corded combi / hammer drills with electronic torque, just do a quick Google search. How accurate they are is down to buying one and using it tbh.

The issue you’ll have with a 230v drill is how big (long) it will be and how few places you can practically utilise it. The above kit for change of £100 will probably do you down to a T, and even though you probably won’t, you could sell it for £60-£80 after you’re done with it. You’re not going to get the tool you want any cheaper than that, I very much doubt, plus this is an impact and a combi!